Use of modified olefin polymers for producing polyolefin products with improved toughness, strength and heat resistance

ABSTRACT

Use of modified olefin polymers for production of polyolefin products with improved toughness, strength and heat resistance. Polyolefin products with high requirements for toughness, strength and heat resistance, produced from modified olefin polymers based on modified propylene polymers which have been modified by reaction with bifunctional monomers in the presence of free-radical generators in the solid phase. The polyolefin products are particularly suitable for shock-absorbing components of motor vehicles, such as bumpers, spoilers and side edge protection elements.

[0001] The invention relates to the use of modified olefin polymersbased on modified propylene polymers for producing polyolefin productswith simultaneously high requirements for toughness and strength andheat resistance.

[0002] Polyolefin products based on propylene polymers with goodtoughness properties are known.

[0003] The toughness of products made of propylene polymers can beimproved by using polypropylene blends which comprise elastomers, suchas polyisobutylene (Martucelli, E., Polymer 24(1983), 1458),ethylene-vinyl acetate copolymers (Thomas, S.,Kautschuk-Gummi-Kunststoffe (Rubbers and Plastics) 40(1987), 665-671 EPR[Greco, R., Polymer 28(1987), 1929-1936], EPDM [Karger-Kocsis, J.,Polymer 23(1982), 699-705] or copolymers made of ethylene and of higherα-olefins [Yu, T., SPE-ANTEC'94, 2439-2442]. The disadvantage of thesemelt blends is a loss of strength and heat resistance with increasingelastomer content.

[0004] It is known to improve the strength and heat resistance inPP/EPDM blends by irradiation with electrons [Gisbergen, J., Polymer30(1989)12, 2153-2157] or in PP/EVA blends [Thomas, S.,Kautschuk-Gummi-Kunststoffe 40(1987), 665-671] and, respectively, inblends made of polypropylene and ethylene-propylene rubber (U.S. Pat.No. 5,459,201) by kneading in the presence of peroxides.

[0005] It is also known to react ethylene polymers, propylene polymers,such as propylene homopolymers or elastomeric propylene-ethylenecopolymers or mixtures of these, with bifunctionally ethylenicallyunsaturated compounds, such as isoprene, in the presence of peroxides inthe melt (EP-A1-0 874 009).

[0006] Impact-modified blends made of polypropylene, of propylenecopolymers with ethylene and/or of higher α-olefins and of elastomericcopolymers made of ethylene and propylene and/or of higher α-olefins,which are prepared by multistage polymerization, are also known (EP-A1-0680 980; EP-A1-0 942 020).

[0007] Polyolefin products with simultaneously high requirements fortoughness and strength and heat resistance have until now required theaddition of large amounts of additives (e.g. 10% by weight of talc asfiller or reinforcing material) to establish the required mechanicalproperties.

[0008] The object of the present invention is to provide polyolefinproducts which satisfy the requirement profile described above and do sousing, in order to establish the required mechanical properties, anamount of additives reduced compared with that used in the prior art.

[0009] According to the invention, this object is then achieved by usingmodified olefin polymers based on modified propylene polymers whicholefin polymers have melt indices of from 8 to 100 g/10 min at 230°C./2.16 kp and are obtainable by activating a polyolefin compositioncomprising

[0010] X % by weight of a semicrystalline propylene homopolymer and/orof a semicrystalline copolymer made of from 88 to 99.5% by weight ofpropylene and from 12 to 0.5% by weight of ethylene and/or an α-olefinof the general formula CH₂═CHR, where R is a linear or branched alkylradical having from 2 to 8 carbon atoms,

[0011] (100-X)% by weight of an elastic copolymer made of from 20 to 70%by weight of ethylene and from 80 to 30% by weight of propylene and/oran α-olefin of the general formula CH₂═CHR₁, where R₁ is a linear orbranched alkyl radical having from 2 to 8 carbon atoms,

[0012] at elevated temperature with peroxides and reacting the activatedpolyolefin composition with 0.1 to 10% by weight, based on thepolyolefin composition, of volatile bifunctional monomers,

[0013] for the production of polyolefin products with simultaneouslyhigh requirements for toughness and strength and heat resistance andhaving the following combinations of properties

[0014] KM₁, KR₁, ZM₁, WF₁ or

[0015] KM₂, KR₂, ZM₂, WF₂ or

[0016] KM₃, KR₃, ZM₃, WF₃ where

[0017] KM₁≧50, KR₁≧50, ZM₁≧350, WF₁≧120 and

[0018] KM₂≧25, KR₂≧40, ZM₂≧700, WF₂≧135 and

[0019] KM₃≧10, KR₃≧30, ZM₃≧1000, WF₃≧145 and where

[0020] KM is Charpy impact strength at −20° C. (kJ/m²) to DIN 53453

[0021] KR is Charpy impact strength at +23° C. (kJ/m²) to DIN 53453

[0022] ZM is tensile modulus at 23° C. (MPa) to DIN 53457/ISO 527

[0023] WF is Vicat A softening point (° C.) to ISO 306,

[0024] and where X takes the values

[0025] X₁=from 60 to 70 for the combination of properties KM₁, KR₁, ZM₁,WF₁;

[0026] X₂=from 70 to 78 for the combination of properties KM₂, KR₂, ZM₂,WF₂,

[0027] X₃ from 78 to 85 for the combination of properties KM₃, KR₃, ZM₃,WF₃.

[0028] Surprisingly, it has been found that mixtures made ofsemicrystalline propylene polymers and of elastomeric ethylenecopolymers in defined mixing ratios, which have been modified byreacting with bifunctional monomers in the presence of free-radicalgenerators, are suitable for the polyolefin products with highrequirements for toughness, strength and heat resistance.

[0029] In this specification the terms “bifunctional monomers” and“bifunctionally unsaturated monomers” have the same meaning, i.e.monomers having (at least) two double bonds.

[0030] The novel polyolefin products are preferably produced usingmodified olefin polymers prepared by

[0031] a) mixing the polyolefin composition, which is in a particulateshape, with from 0.05 to 3% by weight, based on the polyolefincomposition used, of acyl peroxides, alkyl peroxides, hydroperoxides,peresters and/or peroxycarbonates as free-radical generators capable ofthermal decomposition, if desired diluted with inert solvents, withheating to 30-100° C.,

[0032] b) sorption of volatile bifunctional monomers by the particulatepolyolefin composition from the gas phase at a temperature T(° C) offrom 20 to 120° C., where the amount of the bifunctionally unsaturatedmonomers is from 0.01 to 10% by weight, based on the polyolefincomposition used, and then

[0033] c) heating and melting the particulate polyolefin composition inan atmosphere comprising inert gas and/or the volatile bifunctionalmonomers, and from 110 to 210° C., whereupon the free-radical generatorscapable of thermal decomposition are decomposed and then

[0034] d) heating the melt to 220-250° C. in order to remove unreactedmonomers and decomposition products,

[0035] e) pelletizing the melt in a manner known per se.

[0036] In another advantageous embodiment, the novel polyolefin productsare produced from mixtures made of from 85 to 99% by weight of amodified olefin polymer with a melt index of from 8 to 100 g/10 min at230° C./2.16 kp and from 1 to 15% by weight of an unmodified propylenepolymer with a melt index of from 0.5 to 100 g/10 min at 230° C./2.16kp.

[0037] It is preferable here for the unmodified propylene polymers to beformed from propylene homopolymers, from copolymers made of propylenewith α-olefins having from 2 to 18 carbon atoms, preferably from randompropylene copolymers, from propylene block copolymers, from randompropylene block copolymers and/or from elastomeric polypropylenes, orfrom mixtures of the polypropylenes mentioned.

[0038] Particularly suitable propylene homopolymers which may, ifdesired, be present in the novel polyolefin products are propylenehomopolymers with bimodal molar mass distribution, weight-average molarmasses M_(w) of from 500,000 to 1,500,000 g/mol, number-average molarmasses M_(n) of from 25,000 to 100,000 g/mol and M_(w)/M_(n) values offrom 5 to 60, which were prepared in a reactor cascade usingZiegler-Natta catalysts or metallocene catalysts.

[0039] In the preparation of the modified olefin polymers present in thepolyolefin products it has proven advantageous to modify polyolefinparticles directly emerging from the polymerization plant.

[0040] It is preferable for the modified olefin polymers to comprisechemically bonded butadiene, isoprene, dimethylbutadiene, divinylbenzeneor mixtures of these as bifunctionally unsaturated monomers.

[0041] The average sorption time τ_(s) [s] of the volatile bifunctionalmonomers on the particulate polyolefin composition is advantageouslyfrom 10 to 1000 seconds, preferably from 20 to 800 seconds, particularlypreferably from 60 to 600 seconds.

[0042] It is advantageous moreover for the sorption of the volatilebifunctional monomers by the particulate polyolefin composition to takeplace from the gas phase during the preparation of the modified olefinpolymers at a temperature T(° C) of from 70 to 90° C.

[0043] The sorbed amount of the bifunctionally unsaturated monomers inthe modified olefin polymers is preferably from 0.05 to 2% by weight,based on the polyolefin composition used.

[0044] The novel polyolefin products are preferably produced bythermoplastic shaping, in particular by extrusion, injection moulding,blow moulding or thermoforming. Usual processing temperatures for thepolyolefin products produced by extrusion, injection moulding or blowmoulding are ranges of temperature from 170 to 300° C.

[0045] Known production processes for blow-moulded polyolefin mouldingsare extrusion blow moulding, extrusion stretch blow moulding, injectionblow moulding and injection stretch blow moulding (Lee, N., “Plasticblow molding handbook”, Van Norstrand Reinhold Publ. New York 1990;Rosato, D., “Blow molding handbook”, Carl-Hanser-Verlag Munich 1989).

[0046] The injection rate during production of the injection-mouldedpolyolefin products should be set as high as possible, so that thepolyolefin products do not have sink marks or bad flow lines.

[0047] In producing the polyolefin products it is preferable to useinjection moulding machines with injection units which have three-zonescrews with a screw length of from 18 to 24 D.

[0048] The polyolefin products which have been produced by extrusion,injection moulding, blow moulding or thermoforming are suitable for usein the packaging industry, in the household equipment industry, inproducts required in laboratories or in hospitals, in equipment forgardens or agriculture, for transport containers, and also forcomponents in the automotive industry, components of machines andelectrical or electronic equipment.

[0049] Examples of blow-moulded polyolefin products are bottles, smallcontainers, containers for liquids, liquid-feed parts, air-supply systemparts, internal containers, tanks, shock-absorbing components for theautomotive industry, folding bellows, protective covers, housings,tubular components, pipes and/or carrying cases.

[0050] Examples of injection-moulded polyolefin products are componentsin the automotive industry, packaging, transport containers, componentsof machines, of household equipment and of electrical or electronicequipment.

[0051] Particularly preferred polyolefin products are shock-absorbingcomponents of motor vehicles, in particular bumpers, spoilers and sideedge protection elements.

[0052] The following free-radical generators capable of thermaldecomposition may be used during the preparation of the modified olefinpolymers present in the polyolefin products:

[0053] acyl peroxides, such as benzoyl peroxide, 4-chlorobenzoylperoxide, 3-methoxybenzoyl peroxide and/or methylbenzoyl peroxide;

[0054] alkyl peroxides such as allyl tert-butyl peroxide,2,2-bis(tert-butylperoxybutane),1,1-bis(tert-butylperoxy)-3,3,5-trimethylcyclohexane, n-butyl4,4-bis(tertbutylperoxy)valerate, diisopropylaminomethyl tert-amylperoxide, dimethylaminomethyl tert-amyl peroxide, diethylaminomethyltert-butyl peroxide, dimethylaminomethyl tert-butyl peroxide,1,1-di(tert-amylperoxy)cyclohexane, tert-amyl peroxide, tert-butyl cumylperoxide, tert-butyl peroxide, and/or 1-hydroxybutyl n-butyl peroxide;

[0055] peresters and peroxycarbonates, such as butyl peracetate, cumylperacetate, cumyl perpropionate, cyclohexyl peracetate, di-tert-butylperadipate, di-tert-butyl perazelate, di-tert-butyl perglutarate,di-tert-butyl perphthalate, di-tert-butyl persebacate, 4-nitrocumylperpropionate, 1-phenylethyl perbenzoate, phenylethyl nitroperbenzoate,tert-butyl bicyclo[2.2.1]heptanepercarboxylate, tert-butyl4-carbomethoxyperbutyrate, tert-butyl cyclobutanepercarboxylate,tert-butyl cyclohexylperoxycarboxylate, tert-butylcyclopentylpercarboxylate, tert-butyl cyclopropanepercarboxylate,tert-butyl dimethylpercinnamate, tert-butyl2-(2,2-diphenylvinyl)perbenzoate, tert-butyl 4-methoxyperbenzoate,tert-butyl perbenzoate, tert-butyl carboxycyclohexane, tert-butylpernaphthoate, tert-butylperoxy isopropyl carbonate, tert-butylpertoluate, tert-butyl 1-phenylcyclopropylpercarboxylate, tert-butyl2-propylperpenten-2-oate, tert-butyl 1-methylcyclopropylpercarboxylate,tert-butyl 4-nitrophenylperacetate, tert-butylnitrophenylperoxycarbamate, tert-butyl N-succinimidopercarboxylate,tert-butyl percrotonate, tert-butylpermaleic acid, tert-butylpermethacrylate, tert-butyl peroctoate, tert-butylperoxy isopropylcarbonate, tert-butyl perisobutyrate, tert-butyl peracrylate and/ortert-butyl perpropionate; and mixtures of these free-radical generators.

[0056] Volatile bifunctional monomers which may be used in thepreparation of the modified olefin polymers present in the polyolefinproducts are any bifunctionally unsaturated monomeric compounds whichcan be sorbed from the gas phase and can be polymerized with the aid offree radicals. Preference is given to the use of the followingbifunctionally unsaturated monomers in amounts of from 0.01 to 10% byweight, based on the polyolefin mixture used:

[0057] divinyl compounds, such as divinylaniline, m-divinylbenzene,p-divinylbenzene, divinylpentane and/or divinylpropane;

[0058] allyl compounds, such as allyl acrylate, allyl methacrylate,allyl methyl maleate and/or allyl vinyl ether;

[0059] dienes, such as butadiene, chloroprene, cyclohexadiene,cyclopentadiene, 2,3-dimethylbutadiene, heptadiene, hexadiene, isopreneand/or 1,4-pentadiene;

[0060] and mixture of these unsaturated monomers.

[0061] Modified olefin polymers preferably present in the polyolefinproducts are those in which the bifunctionally unsaturated monomerpresent is chemically bonded butadiene, isoprene, dimethylbutadieneand/or divinylbenzene.

[0062] Continuous gas-solid absorbers used for the sorption of thevolatile bifunctional monomers in the preparation of the modified olefinpolymers are preferably continuous through-flow mixers.

[0063] During the preparation of the modified olefin polymers, theheating and melting of the polyolefin particles within which thebifunctionally unsaturated monomers and the acyl peroxides, alkylperoxides, hydroperoxides, peresters and/or peroxycarbonates have beensorbed as free-radical generators capable of thermal decomposition takesplace in an atmosphere of the volatile bifunctionally unsaturatedmonomers, preferably in continuous kneaders or extruders, withpreference in twin-screw extruders.

[0064] The modified olefin polymers and, respectively, the mixtures madeof modified olefin polymers and of unmodified propylene polymers maycomprise, as additives, from 0.01 to 2.5% by weight of stabilizersand/or from 0.1 to 1% by weight of antistats and/or from 0.2 to 3% byweight of pigments and/or from 0.05 to 1% by weight of nucleating agentsand/or from 1 to 40% by weight of fillers and/or reinforcing materialsand/or from 2 to 20% by weight of flame retardants and/or from 0.01 to1% by weight of processing aids, based on the modified olefin polymersand, respectively, the mixtures made of modified olefin polymers and ofunmodified propylene polymers.

[0065] Stabilizers which may be present in the modified olefin polymersor in the mixtures made of modified olefin polymers and of unmodifiedpropylene polymers are preferably mixtures made of from 0.01 to 0.6% byweight of phenolic antioxidants, from 0.01 to 0.6% by weight offree-arylbenzofuranones, from 0.01 to 0.6% by weight of processingstabilizers based on phosphites, from 0.01 to 0.6% by weight ofhigh-temperature stabilizers based on disulphides and on thioethersand/or from 0.01 to 0.8% by weight of sterically hindered amines (HALS).

[0066] Suitable phenolic antioxidants are2-tert-butyl-4,6-dimethylphenol, 2,6-di-tert-butyl-4-methylphenol,2,6-di-tert-butyl-4-isoamylphenol, 2,6-di-tert-butyl-4-ethylphenol,2-tert-butyl-4,6-diisopropylphenol, 2,6-dicyclopentyl-4-methylphenol,2,6-di-tert-butyl-4-methoxymethylphenol,2-tert-butyl-4,6-dioctadecylphenol, 2,5-di-tertbutylhydroquinone,2,6-di-tert-butyl-4-dihexadecyloxyphenol,2,2′-methylenebis(6-tert-butyl-4-methylphenol),4,4′-thiobis(6-tert-butyl-2-methylphenol), octadecyl3-(3,5-di-tert-butyl-4-hydroxyphenyl)propionate,1,3,5-trimethyl-2,4,6-tris(3′,5′-di-tert-butyl-4-hydorxybenzyl)benzeneand/or pentaerythritoltetrakis[3-(3,5-di-tert-butyl-4-hydroxyphenyl)]propionate.

[0067] A particularly suitable benzofuranone derivative is5,7-di-tert-butyl-3-(3,4-dimethylphenyl)-3H-benzofuran-2-one.

[0068] Particularly suitable HALS compounds arebis-2,2,6,6-tetramethyl-4-piperidyl sebacate and/orpoly((6-((1,1,3,3-tetramethylbutyl)amino)-1,3,5-tdazine-2,4-diyl)(2,2,6,6-tetramethyl-4-piperidyl)imino)-1,6-hexanediyl((2,2,6,6-tetramethyl-4-piperidyl)imino))-.

[0069] Nucleating agents which may be present in the modified olefinpolymers or in the mixtures made of modified olefin polymers and ofunmodified propylene polymers are α-nucleating agents, such as talc orsodium methylenebis(2,4-di-tert-butylphenyl)phosphate β-nucleatingagents, such as the dianilide of adipic acid or dibenzoquinacridone orN,N′-dicyclohexyl-2,6-naphthalenedicarboxamide.

[0070] The fillers which may, if desired, be present in the modifiedolefin polymers or mixtures made of modified olefin polymers and ofunmodified propylene polymers are preferably Al₂O₃, Al(OH)₃, bariumsulphate, calcium carbonate, glass beads, wood flour, siliceous earth,hollow microbeads, carbon black, talc and/or wollastonite.

[0071] The reinforcers which may, if desired, be present in the modifiedolefin polymers or mixtures made of modified olefin polymers and ofunmodified propylene polymers are preferably aramid fibres, cellulosefibres, flax, jute, kenaf, glass fibres, microfibres made ofliquid-crystalline polymers and/or polytetrafluoroethylene fibres.

[0072] Processing aids which may be present in the modified olefinpolymers or in the mixtures made of modified olefin polymers and ofunmodified propylene polymers are calcium stearate, magnesium stearateand/or waxes.

[0073] The novel polyolefin products preferably have gel contents offrom 0.5 to 20% by weight.

EXAMPLES

[0074] The examples below illustrate the invention:

Example 1

[0075] Preparation of the Modified Olefin Polymer:

[0076] A pulverulent polyolefin mixture (melt index 13 g/10 min at 230°C./2.16 kp, average particle diameter 0.55 mm) made of 73% by weight ofa propylene homopolymer (melt index 28 g/10 min at 230° C./2.16 kp) and27% by weight of an ethylene-propylene copolymer (ethylene content 14.3%by weight) is metered continuously into a continuous heatablethrough-flow mixer. 0.1% by weight of calcium stearate and 0.09% byweight of bis(tert-butylperoxy)-2,5-dimethylhexane, based in each caseon the polyolefin mixture, are then metered continuously into thethrough-flow mixer. With thorough and homogeneous mixing at 45° C., thepolyolefin mixture, loaded with free-radical generator capable ofthermal decomposition and with auxiliary, is loaded by sorption with0.92% by weight of divinylbenzene, based on the polyolefin mixture,using a divinylbenzene-nitrogen mixture with a residence time of 6 minat 82° C. The pulverulent reaction mixture is transferred to a Berstorfftwin-screw extruder (temperature profile25/160/160/160/165/160/190/220/220/230° C., throughput 5.8 kg/h) and, incontact with the divinylbenzene-nitrogen mixture metered in, and withaddition of 0.1% by weight of tetrakis[methylene(3,5-di-tert-butylhydroxyhydrocinnamate)]methane and 0.1% by weight oftris(2,4-di-tert-butylphenyl) phosphite, heated and melted, subjected topreliminary devolatilization with water metered in as entrainer and thento intensive devolatilization, discharged and pelletized.

[0077] The resultant modified olefin polymer has a content of bondeddivinylbenzene of 0.7% by weight, determined by IR spectroscopy, and amelt index of 14.2 g/10 min at 230° C./2.16 kp.

[0078] Production of Injection Mouldings from the Modified OlefinPolymer:

[0079] The pellets prepared are processed in a Ferromatic Millacron FM60 injection moulding machine which has a three-zone screw with a screwlength of 22 D, at a melt temperature of 225° C. and with a mouldtemperature of 50° C., according to DIN 16774, to give standardinjection-moulded test specimens.

[0080] The Following Properties Were Determined on the StandardInjection-Moulded Test Specimens:

[0081] Charpy impact strength at −20° C. to DIN 53453: 38 kJ/m²

[0082] Charpy impact strength at +23° C. to DIN 53453: 57 kJ/m²

[0083] Tensile modulus at 23° C. to DIN 53457/ISO 527: 800 MPa

[0084] Vicat A softening point (° C.) to ISO 306: 138° C.

Example 2

[0085] Preparation of the Modified Olefin Polymer:

[0086] A pulverulent polyolefin mixture (melt index 0.5 g/10 min at 230°C./2.16 kp, average particle diameter 0.26 mm) made of 75% by weight ofa propylene-ethylene copolymer (melt index 0.45 g/10 min at 230° C./2.16kp, ethylene content 5.5% by weight) and 25% by weight of anethylene-propylene copolymer (ethylene content 12.5% by weight) ismetered continuously into a continuous heatable through-flow mixer. 0.1%by weight of magnesium stearate and 0.25% by weight of tert-butylperoxyisopropyl carbonate, based in each case on the polyolefin mixture,are then metered continuously into the through-flow mixer. With thoroughand homogeneous mixing at 52° C., the polyolefin mixture, loaded withfree-radical generator capable of thermal decomposition and withauxiliary, is loaded by sorption with 0.3% by weight of isoprene, basedon the polyolefin mixture, using a isoprene-nitrogen mixture with aresidence time of 5 min at 76° C. The pulverulent reaction mixture istransferred to a Berstorff twin-screw extruder (temperature profile25/150/155/160/160/160/185/215/220/220° C., throughput 5.2 kg/h) and, incontact with the isoprene-nitrogen mixture metered in, and with additionof 0.1% by weight of 2,2′-methylenebis(6-tert-butyl4-methylphenol) and0.1% by weight of5,7-di-tert-butyl-3-(3,4-dimethylphenyl)3H-benzofuran-2-one, heated andmelted, subjected to preliminary devolatilization with water metered inas entrainer and then to intensive devolatilization, discharged andpelletized.

[0087] The resultant modified olefin polymer has a content of 0.22% byweight of bonded isoprene, determined by IR spectroscopy, and a meltindex of 8.2 g/10 min at 230° C./2.16 kp.

[0088] A compound made of 90% by weight of the modified olefin polymerand 10% by weight of an unmodified propylene homopolymer (melt index 28g/10 min at 230° C./2.16 kp) is extruded through a Brabender laboratoryextruder with slot die (temperature profile 85/150/185/220/220/220° C.)to give a rectangular 40×4 mm profile.

[0089] Stamped-Out Test Specimens Have the Following Properties:

[0090] Charpy impact strength at −20° C. to DIN 53453: 28 kJ/m²

[0091] Charpy impact strength at +23° C. to DIN 53453: 48 kJ/m²

[0092] Tensile modulus at 23° C. to DIN 53457/ISO 527: 710 MPa

[0093] Vicat A softening point (° C) to ISO 306: 136° C.

Example 3

[0094] Preparation of the Modified Olefin Polymer:

[0095] A pulverulent polyolefin mixture (melt index 6 g/10 min at 230°C./2.16 kp, average particle diameter 0.32 mm) made of 65% by weight ofa propylene copolymer (melt index 17 g/10 min at 230° C./2.16 kp) and35% by weight of an ethylene-propylene copolymer (ethylene content 18.2%by weight) is metered continuously into a continuous heatablethrough-flow mixer. 0.1% by weight of montan wax and 0.18% by weight ofmethyl benzoyl peroxide, based in each case on the polyolefin mixture,are also metered continuously into the through-flow mixer. With thoroughand homogeneous mixing at 45° C., the polyolefin mixture, loaded withfree-radical generator capable of thermal decomposition and withauxiliary, is loaded by sorption with 0.45% by weight of butadiene,based on the polyolefin mixture, using a butadiene-nitrogen mixture witha residence time of 4 min at 88° C. The pulverulent reaction mixture istransferred to a Berstorff twin-screw extruder (temperature profile25/150/160/160/165/170/190/220/220/230° C., throughput 6.2 kg/h) and, incontact with the butadiene-nitrogen mixture metered in, and withaddition of 0.1% by weight of 2-tert-butyl-4,6-dioctadecylphenol and0.1% by weight of tris(2,4-di-tert-butylphenyl) phosphite, heated andmelted, subjected to preliminary devolatilization with water metered inas entrainer and then to intensive devolatilization, discharged andpelletized.

[0096] The resultant modified olefin polymer has a content of bondedbutadiene of 0.36% by weight, determined by IR spectroscopy, and a meltindex of 14.2 g/10 min at 230° C./2.16 kp.

[0097] Production of a Container With a Square Base:

[0098] The modified olefin polymer (melt index 14.2 g/10 min at 230°C./2.16 kp) is melted using the temperature profile 100/160/205/215/215°C. in the plastifying unit of an injection stretch blow moulding machinecomprising plastifying unit with three-zone screw, rotary table withcooled 4-fold injection mould, conditioning mould with three heatingzones, blow mould with stretching ram and ejection apparatus, andinjected into the 4-fold injection mould, temperature-controlled to 120°C. The parison (31 g, wall thickness from 4.5 to 5.5 mm, height 88 mm)is removed from the injection mould by way of the mandrel of the rotarytable and introduced into the electrically heated conditioning mould byway of a 90° tipping movement of the rotary table, the heating zones ofthe conditioning mould having been set at 135° C. (parison base), 138°C. (parison central section) and 135° C. (parison upper section). Aftera conditioning time of 80 s compressed air is used for preblowing, theblow-moulded premoulding is removed and transferred, by way of themandrel of the rotary table and the 900 tipping movement of the rotarytable, into the blow mould, where the blow-moulded premoulding is thensubjected to longitudinal stretching by way of the stretching ram andthen shaped using compressed air at a pressure of 20 bar. Thelongitudinal stretching ratio for the premoulding in the blow mould is2.8:1 and the transverse stretching ratio for the premoulding is 2.0:1.The blow-moulded container is removed from the opened blow mould after7.5 s, fed to the ejector by way of a 90° tipping movement of the rotarytable, and ejected.

[0099] Test Specimens Stamped out From the Sides of the Container Havethe Following Properties:

[0100] Charpy impact strength at −20° C. to DIN 53453: 67 kJ/m²

[0101] Charpy impact strength at +23° C. to DIN 53453: 74 kJ/m²

[0102] Tensile modulus at 23° C. to DIN 53457/ISO 527: 550 MPa

[0103] Vicat A softening point (° C.) to ISO 306: 125° C.

Example 4

[0104] Preparation of the Modified Olefin Polymer:

[0105] A pulverulent polyolefin mixture (melt index 8.5 g/10 min at 230°C./2.16 kp, average particle diameter 0.28 mm) made of 82% by weight ofa propylene-ethylene copolymer (melt index 14 g/10 min at 230° C./2.16kp, ethylene content 8.2% by weight) and 18% by weight of anethylene-propylene copolymer (ethylene content 28.5% by weight) ismetered continuously into a continuous heatable through-flow mixer.0.15% by weight of calcium stearate and 0.35% by weight of tert-butylcyclopentylpercarboxylate, based in each case on the polyolefin mixture,are then metered continuously into the through-flow mixer. With thoroughand homogeneous mixing at 50° C., the polyolefin mixture, loaded withfree-radical generator capable of thermal decomposition and withauxiliary, is loaded by sorption with 0.82% by weight ofdimethylbutadiene, based on the polyolefin mixture, using adimethylbutadiene-nitrogen mixture with a residence time of 5.5 min at72° C. The pulverulent reaction mixture is transferred to a Berstorfftwin-screw extruder (temperature profile25/160/160/160/165/160/190/220/220/230° C., throughput 5.4 kg/h) and, incontact with the dimethylbutadiene-nitrogen mixture metered in, and withaddition of 0.15% by weight of 4,4′-thiobis(6-tert-butyl-2-methylphenol)and 0.1% by weight of sodium methylenebis(2,4-di-tert-butylphenol)phosphate, heated and melted, subjected to preliminary devolatilizationwith water metered in as entrainer and then to intensivedevolatilization, discharged and pelletized.

[0106] The resultant modified olefin polymer has a content of bondeddimethylbutadiene of 0.70% by weight, determined by IR spectroscopy, anda melt index of 8.2 g/10 min at 230° C./2.16 kp.

[0107] Production of Injection Mouldings From the Modified Olefinpolymers:

[0108] The pellets produced are processed in a Ferromatic Millacron FM60 injection moulding machine which has a three-zone screw with a screwlength of 22 D, at a melt temperature of 225° C. and at a mouldtemperature of 50° C., in accordance with DIN 16774, to give standardinjection moulded test specimens.

[0109] The Following Properties Were Determined on the StandardInjection Moulded Test Specimens:

[0110] Charpy impact strength at −20° C. to DIN 53453: 12 kJ/m²

[0111] Charpy impact strength at +23° C. to DIN 53453: 34 kJ/m²

[0112] Tensile modulus at 23° C. to DIN 53457/ISO 527: 1120 MPa

[0113] Vicat A softening point (° C.) to ISO 306: 147° C.

1. Use of modified olefin polymers based on modified propylene polymers which olefin polymers have melt indices of from 8 to 100 g/10 min at 230° C./2.16 kp and are obtainable by activating a polyolefin composition comprising X % by weight of a semicrystalline propylene homopolymer and/or of a semicrystalline copolymer made of from 88 to 99.5% by weight of propylene and from 12 to 0.5% by weight of ethylene and/or an α-olefin of the general formula CH₂═CHR, where R is a linear or branched alkyl radical having from 2 to 8 carbon atoms, (100-X)% by weight of an elastic copolymer made of from 20 to 70% by weight of ethylene and from 80 to 30% by weight of propylene and/or an α-olefin of the general formula CH₂═CHR₁, where R₁ is a linear or branched alkyl radical having from 2 to 8 carbon atoms, at elevated temperature with peroxides and reacting the activated polyolefin composition with 0.1 to 10% by weight, based on the polyolefin composition, of volatile bifunctional monomers, for the production of polyolefin products with simultaneously high requirements for toughness and strength and heat resistance and having the following combinations of properties KM₁, KR₁, ZM₁, WF₁ or KM₂, KR₂, ZM₂, WF₂ or KM₃, KR₃, ZM₃, WF₃ where KM₁≧50, KR₁≧50, ZM₁≧350, WF₁≧120 and KM₂≧25, KR₂≧40, ZM₂≧700, WF₂≧135 and KM₃≧10, KR₃≧30, ZM₃≧1000, WF₃≧145 and where KM is Charpy impact strength at −20° C. (kJ/m²) to DIN 53453 KR is Charpy impact strength at +23° C. (kJ/m²) to DIN 53453 ZM is tensile modulus at 23° C. (MPa) to DIN 53457/ISO 527 WF is Vicat A softening point (° C.) to ISO 306, and where X takes the values X₁=from 60 to 70 for the combination of properties KM₁, KR₁, ZM₁, WF₁; X₂=from 70 to 78 for the combination of properties KM₂, KR₂, ZM₂, WF₂; X₃=from 78 to 85 for the combination of properties KM₃, KR₃, ZM₃, WF₃.
 2. Use according to claim 1, characterized in that the modified olefin polymers are prepared by a) mixing the polyolefin composition, which is in a particulate shape, with from 0.05 to 3% by weight, based on the polyolefin composition used, of acyl peroxides, alkyl peroxides, hydroperoxides, peresters and/or peroxycarbonates as free-radical generators capable of thermal decomposition, if desired diluted with inert solvents, with heating to 30-100° C., b) sorption of volatile bifunctional monomers by the particulate polyolefin composition from the gas phase at a temperature T(° C.) of from 20 to 120° C., where the amount of the bifunctionally unsaturated monomers is from 0.01 to 10% by weight, based on the polyolefin composition used, and then c) heating and melting the particulate polyolefin composition in an atmosphere comprising inert gas and/or the volatile bifunctional monomers, and from 110 to 210° C., whereupon the free-radical generators capable of thermal decomposition are decomposed and then d) heating the melt to 220-250° C. in order to remove unreacted monomers and decomposition products, f) pelletizing the melt in a manner known per se.
 3. Use according to claim 1 or 2 characterized in that the polyolefin products are produced from mixtures made of from 85 to 99% by weight of a modified olefin polymer with a melt index of from 8 to 100 g/10 min at 230° C./2.16 kp and from 1 to 15% by weight of an unmodified propylene polymer with a melt index of from 0.5 to 100 g/10 min at 230° C./2.16 kp.
 4. Use according to claim 3, characterized in that the unmodified propylene polymers are formed from propylene homopolymers, from copolymers made of propylene with α-olefins having from 2 to 18 carbon atoms, preferably from random propylene copolymers, from propylene block copolymers, from random propylene block copolymers and/or from elastomeric polypropylenes, or from mixtures of the polypropylenes mentioned.
 5. Use according to any one of claims 1 to 4, characterized in that the modified olefin polymers comprise chemically bonded butadiene, isoprene, dimethylbutadiene, divinylbenzene or mixtures of these as bifunctionally unsaturated monomers.
 6. Use according to any one of claims 2 to 5, characterized in that the average sorption time τ_(s) [s] of the volatile bifunctional monomers on the particulate polyolefin composition is from 10 to 1000 seconds, preferably from 20 to 800 seconds, particularly preferably from 60 to 600 seconds.
 7. Use according to any one of claims 2 to 6, characterized in that the sorption of the volatile bifunctional monomers by the particulate polyolefin composition takes place from the gas phase during the preparation of the modified olefin polymers at a temperature T(° C.) of from 70 to 90° C.
 8. Use according to any one of claims 2 to 7, characterized in that the sorbed amount of the bifunctionally unsaturated monomers in the modified olefin polymers is from 0.05 to 2% by weight, based on the polyolefin composition used.
 9. Use according to any one of claims 1 to 8, characterized in that the polyolefin products are produced by thermoplastic shaping, in particular extrusion, injection moulding, blow moulding or thermoforming.
 10. Use according to any one of claims 1 to 9, characterized in that the polyolefin products are designed as shock-absorbing components of motor vehicles, in particular bumpers, spoilers and side edge protection elements.
 11. Use according to any one of claims 1 to 10, characterized in that the polyolefin products have gel contents of from 0.5 to 20% by weight.
 12. Polyolefin products obtained by a use according to any one of claims 1 to
 11. 